Typical voice codecs such as those used in mobile phones and Voice Over IP (VOIP) networks encode an original speech signal using a scheme designed for improving perceptual quality for human listeners, not for speech recognition performance. In contrast, speech recognition systems often encode voice recognition features, such as representations of warped frequency spectral estimates (also referred to herein as warped spectral estimates), using a scheme designed for improving speech recognition performance. Some schemes have attempted to use encoded speech recognition features to construct audio signals, and some schemes have attempted to use encoded voice codec features to perform speech recognition.